1. Field of the Invention
The present invention relates to a method for joining foil hoses that are subdivided in bag portions according to the pitch of the bag length and a device for realizing this method.
It is known to produce packing bags by first making a foil hose that is subsequently printed and subdivided by transverse welds into individual portions forming bags. Afterwards, the foil hose is reeled up by a winding device to form a roll. The separation of the individual bags from the foil hose and the filling of these bags is effected in a filling and closing apparatus fed by the foil hose roll.
Difficulties occur upon the joining of two foil hoses. Such joining is necessary, if the foil hose roll that feeds the filling and closing apparatus is used up and the beginning of a new foil hose roll is to be placed at the end of the old foil hose roll. Another reason for the joining of foil hoses may be that a foil hose shows imperfections that have to be cut out. According to prior art, the joining of foil hoses is achieved by superimposing the respective hose ends with a comparatively large overlapping area and by applying a comparatively wide adhesive tape on both sides of the overlapping foil hoses. Applying these tapes requires considerable skill and comparatively much time. However, it is an even more serious problem that the respective bag portion, in which the joining has taken place, is of lessened quality and has to be subsequently removed from the production line as waste. This is particularly disadvantageous if the bags are fed to a filling and closing apparatus. If the goods to be filled into the bags have to be filled in under sterile conditions, as is true for example with diapers, the bags provided with adhesive tape have to be especially marked. These bags may be filled by the filling and closing apparatus, but they have to be subsequently sorted as waste together with the filling.
It is an object of the invention to provide a method that allows to join or combine foil hoses subdivided into bag portions such that no bag of insufficient quality occurs at the joint and that, in particular, a joining by adhesive tape is avoided.
This object is solved with the features of claim 1.
In the method according the present invention, two corresponding transverse welds of the foil hoses to be joined are superimposed and joined together by means of a joining weld. Thus, the foil hoses are joined at places, that are provided with transverse welds, anyway, i.e., the already existent transverse welds are covered with the joining weld. The joining weld is situated at a place in the pitch of the bag portions that is already provided with a transverse weld. This results in a joint that is practically different from the usual transverse welds. The only difference is that the thickness at the joining weld of the joined foil hose is greater than that at the welds of the simple foil hose; however, this greater thickness is hardly perceptible in the end product, due to the pressure applied during the welding. The method according to the invention allows a simple and rapid joining of foil hoses in the pitch of the bag portions, without impairing the quality of the respective bag portion at the joint. The method may be applied if a foil hose leaves the bag making machine in which the transverse welds for the individual bag portions are provided, and before the foil hose is reeled up to form a roll.
In the case of the foil hose being torn off or showing imperfections, it is possible to join the respective hose ends, so that rolls of a predetermined size can be reeled up at any time, without the roll having bag portions with adhesive tape. Another application of the present method is effected in combination with a filling and closing apparatus to which a foil hose is supplied from a roll. There is the particular possibility of rapidly joining the end of one roll to the beginning of the next roll without any loss in quality. Thus, the troublesome lacing-up of the beginning of the new roll into the filling and closing apparatus that usually requires an overmeasure of about 20 to 25 meters of hose length may be dropped.
The method according to the present invention is particularly suited for the processing of foil hoses for satchel bags with a flat portion of the bag having a grip hole provided between an upper end weld and an intermediate weld. With such satchel bags, the joining welding is performed at the superimposed intermediate welds, i.e., in the central longitudinal part of the bag and not at one of the end welds.
A device for performing the method according to the present invention is provided with a transverse-welding station arranged at a spot, where each transverse weld of the intermittently moved foil hose stops. This allows to draw only one of the foil hoses to be joined up to the transverse-welding station, while the other foil hose is already in the correct position at the transverse-welding station.
The transverse-welding station may be of a very simple configuration. It requires only two welding bars that provide the joining weld over the already existing transverse welds. These welding bars may be simultaneously provided with cutting edges for tearing off the flaps of the joined foil hoses.
A detailed description of preferred embodiments of the invention will be made with reference to the accompanying drawings.